1. Field of the Invention
Certain heterocyclic ureas are useful in protecting plants from the deleterious effects of atmospheric ozone. Ozone is a common air pollutant around urban areas which has been found to damage crop plants, ornamental plants and shade and forest trees. Polluted air is estimated to cost farmers a half-billion dollars a year. Even air that contains a level of ozone below that common to urban areas reduces yields of many crops.
2. Description of the Prior Art
Ureas have been widely employed for selective biological activity. Some have been suggested for pharmacological uses, e.g. Shoeb et al. [C.A. 68, 12946e (1968)] propose 1-phenyl-3-(2-pyridylethyl) ureas to lower blood sugar. Others such as ##STR2## i.e., 5-(3-phenylureido)-1,3-dimethylpyrazole, have been found effective as plant defoliants in U.S. Pat. No. 3,646,059. 1-Morpholino-3-phenylurea has been shown to have cytokinin activity in a cellular assay [Bruce, Proc. Roy. Soc (London) Ser. B 165 (1966) 245-265]. Many have found application as herbicides, but none have been reported to be useful in protecting plants against atmospheric ozone.